The overall aim of this work is to use chitosan and its derivatives as polymeric carriers for sustained release of drugs that contained carboxylic functional group. Three types of drugs are chosen for this study: (1) antibacterial agents-quinolone carboxylic acids-nalidixic acid, piromidic acid, oxolinic acid, cinoxacin, droxacin, flumequine, and rosoxacin, (2) anti-inflammatory agents-aspirin, ibuprofen, and naproxen, and (3) antibiotic agents-tubermycin B, amoxicillin, and benzylpenicillinic acid. Three techniques will be used to carry out the comparative study of the sustained release of these drugs under the simulated gastric and intestinal fluids. These techniques include the direct compression of drugs into the polymeric matrices of chitosan or its derivatives, the wet granulation of drugs with chitosan or its derivatives, and the conversion of drugs containing carboxylic acid functional group to N-acyl and/or O-acyl derivatives of chitosan. A comprehensive study and careful measurements of the rates of these selected drugs' release from chitosan or its derivatives will provide valuable data which may allow one to select the best methods in formulating drugs for prolonged action.